The last time I was here to review an episode of Doctor Who (too long ago, for which I apologize), it was a really good day. “The Girl Who Died” was another high point for Series 9, and for co-writer Jamie Mathieson, and at this point I can’t be the only one who’d like to see him back with another script or two every season.

But the show should always keep room for new talent. And so the second part of Ashildr’s story was written by Catherine Tregenna, a Torchwood veteran working on her first Doctor Who script. Given her experience, I’m surprised and a little disappointed that it took so long to have her on the show.

And given the story she crafted, I really hope it won’t take so long to bring her back.

Although it follows the story Mathieson and Steven Moffat began in “The Girl Who Died,” “The Woman Who Lived” isn’t a strict Part 2 as we understand it. It doesn’t continue the plot of the previous episode (the only “Part 1” not to end in a true cliffhanger) so much as it tells a new story with the same themes and the same character.

Centuries after he left her to live, Twelve finds the young woman he once knew as Ashildr. And so much has changed since he granted her the gift/curse of immortality (everyone who ever writes about immortality is legally bound to refer to it as both). All that living among other humans has made her much less of one. Too much pain, too much unimaginable loss, has sapped away her empathy and emotion. Now, she lives as a highwayman, taking the name of “Me,” living only for herself.

To that end, she has aligned herself with an alien being who has promised her escape in exchange for an Object Of Great Power. And of course that being is only using it and her for his own evil designs. But none of that is really important here, except as a way to the heart of the story. And the heart of “The Woman Who Lived” is a character study. It’s about what life and death make you. It’s about trying to be human when you’re really not.

Almost from the moment they meet again, Twelve is horrified at what Ashildr has become. And he’s even more horrified to realize his part in making her so. So he tries to reawaken her humanity, to make her care again, even as she reminds him of the consequences of his own caring, of what happens to the people he saves and leaves behind.

These confrontations take up most of the episode. Tregenna’s writing digs deep, forcing both Ashildr and Twelve to confront the most painful parts of themselves. And just like her, Maisie Williams and Peter Capaldi dig deeper. Their scenes together are one more testament to the power of great actors and great writing to elevate a scene into something truly powerful.

As you can imagine, there isn’t a whole lot of humor to these moments. But Tregenna knows what she’s doing. Early in the episode, Ashildr/Me/the Knightmare encounters her rival, the ribald and ineffectual Sam Swift (a wonderful performance by Rufus Hound). We think nothing of him – he’s clearly just there for comic relief, right?

Of course, he isn’t. When we see him again, he’s facing death, and the obligatory fate worse than it. And he’s facing it with the same humor and grace – even on the gallows, he’s still joking. And when Twelve joins in, he’s truly grateful to have an audience. It’s literally what he’s living for.

The lesson to Ashildr is pretty clear and pretty obvious. Because he knows he’s about to die, Sam values life more than anyone in that moment. It’s the fact that life ends that makes it worth living, and worth saving. And so Me becomes Ashildr again, and makes the choice to save him, and the Earth with him.

But once again, we’re left with messy consequences. In the name of saving him, Ashildr has just done to Sam what Twelve once did to her. And we’re not sure if he can handle it. So she’s resolved to stick around after the Doctor leaves, to care for those he’s not around to care for any longer. It’s kind of a promise. It’s kind of a threat. It’s kind of both.

And it’s a guarantee that we’ll see her again.

At the halfway point of the season (well, we’re actually past the halfway point now, but I’ll get to that in my next review), I’m pretty thrilled with Doctor Who right now. The longer stories have worked – plots are allowed to develop more fully, and characters are explored more deeply by both the writers and the actors. It’s really something to behold.

And with that, I’ll end this review. I’ll be back with a review of the Zygon story that’s wrapping up tonight (I enjoyed “The Zygon Invasion” last week, but given that it’s a true two-parter, I’m probably better off reviewing the whole story at once this time).

So, until then…